Tension-controlling means



United States Patent 3,141,627 TENSION-CONTROLLING MEANS Esteban Martinez, Princeton, NJ.

(126 Montgomery St., Apt. 3-D, Highland Park, NJ.) Filed Aug. 22, 1962, Ser. No. 218,711 5 Claims. (Cl. 24275.47)

This invention relates to sensing and control means and is directed particularly to constructions adapted for use in controlling the tension applied to a travelling Web, strip or strand of material such as paper, metal or plastic foil, textile material, wire, thread or the like.

It is usual in the paper industry and elsewhere to provide some form of control means to maintain the tension applied to the web of material constant so as to avoid breakage of the web and resulting loss in time to rethread the machine and restart the operation. One of the principal causes for the changes in tension which normally occur in winding, unwinding or reeling operations arises from the changes in diameter of a roll from which a web of material is being drawn or on which it is being wound. Such changes occur continuously rendering it very difiicult to maintain a constant and uniform tension on the material at all times.

It has been common practice heretofore to control the tension on a web of material by providing a dancer roll or other element which engages the web and is movable in response to a change in tension on the web to actuate a brake or other control means for the roll. However, there is a necessary lag in the response of such equipment since the tension must change before the dancer roll or other sensing element is actuated. Moreover, if the web of material is wet, printed or coated with an adhesive or other material, the web or its coating may be damaged by engagement of the dancer roll therewith. Furthermore, such control means are not readily applied to different types of web-handling equipment or easily changeable from one machine to another.

In accordance with the present invention, these objections and limitations inherent in control devices of the prior art are overcome and equipment is provided which is simple and inexpensive to construct and operate and which serves to aiford continuous and automatic control in a manner to maintain the tension applied to a Web of material substantially constant. The equipment does not include any element which engages the web and may be applied interchangeably to various types of winding, reeling and web-handling equipment. It is also capable of operation at a point remote from the equipment being controlled so that it can be located at any convenient point without interfering with other elements of the assembly.

These advantages are preferably attained by providing a pneumatically actuated system wherein the pressure is varied in response to the speed of rotation of a shaft and control means operated by the system are employed to actuate a brake or other means by which the tension applied to the web may be controlled.

Accordingly, the principal object of the invention is to provide a novel type of sensing and control means for web-handling equipment which is operable to afford continuous and accurate control 'of the tension applied to the web.

A further object of the invention is to provide speed responsive means for controlling the operation of webhandling'equipment or the like.

A specific object of the invention is to provide a pneumatic system wherein the pressure of a gas is varied in' response to the speed of rotation of a shaft and is ice utilized for controlling the operation of equipment to which the invention is applied.

These and other objects of the present invention will appear from the following description thereof wherein reference is made to the figures of the accompanying drawing.

In the drawing:

FIG. 1 is a diagrammatic illustration of a typical form of control system embodying the present invention; and

FIG. 2 is a diagrammatic illustration of an alternative embodiment of the invention.

In that form of the invention chosen for purposes of illustration in the drawing, the system is designed to control the tension applied to a web of material 2 which travels from a supply roll 4 to a take-up roll 6 in the direction of the arrow. The take-up roll 6 is driven by a motor 8 or the other suitable means whereas the shaft 10 upon which the supply reel 4 is mounted is provided with a braking device 12. The braking device shown for purposes of illustration has brake shoes 14 pivotally connected at 16 and engageable with a brake drum 18 secured to the shaft 10 of the supply roll. A pneumatically actuated device such as the cylinder 20 is actuated to vary the operation of the brake shoes 14 whereby the tension applied to the web of material 2 may be maintained constant.

The pressure of the air or gas supplied to the cylinder 20 and the action of the braking means, such as brake shoes 14, is varied in response to the speed of rotation of the shaft 10. This speed in turn will, of course, depend upon the diameter of the supply roll 4. Therefore, in order to maintain a uniform tension on the web of material 2, the braking device 12 should exert a greater force opposing rotation of the supply roll 4 when its diameter is relatively large than when its diameter has been reduced. Thus, the braking eifect should be varied in direct proportion to the diameter of the roll 4 and in inverse proportion to the speed of rotation of the shaft 10.

In order to attain this effect in accordance with the present invention, the pressure of the air supplied to the brake cylinder 20 is controlled by a valve 22 in the air exhaust line 24 of an air reservoir 26. The valve 22 is actuated by the shaft 10 through suitable means, such as a crank 28, whereby the valve 22 is opened momentarily once, or a predetermined number of times, upon each complete revolution of the shaft 10. The air in air reservoir 26 is supplied from a relatively high pressure air pump 30 to the air line 32 through a suitable capillary, needle valve, orifice or other resistance means 34 which serves to meter the flow of air to the air reservoir 26 and to eliminate or reduce pulsations or other variations in pressure due to the operation of pump 30. At the same time, the valve 22 controls the rate at which air is released from air reservoir 26. The pressure existing in the air reservoir 26 is, therefore, determined by the difference in the inflow of gas to reservoir 26 from pump 30 and the outflow of gas through exhaust line 24 under the control of valve 22.

From the resevoir 26 air is supplied though the line 36 to a suitable filtering or smoothing arrangement such as the resistance means or capillary 38 and a capacity chamber 40. The air from chamber 40 is supplied to the brake cylinder 20 through the conduit 42 to vary the force urging the brake shoes 14 against the brake drum 18.

In operating such a system, the pressure of the air supplied to the reservoir 26 by pump 30 may be of the order of pounds per square inch for example but, of course, can be chosen to meet any desired operating conditions. The pressure Within the reservoir itself will, however, vary depending upon the adjustment and frequency of operation of the valve 22 by the shaft of the supply roll 4. If the shaft rotates slowly and the valve 22 is operated at infrequent intervals, the pressure in reservoir 26 will build up and approach 100 pounds or that for which a relief valve 44- may be adjusted. However, if the shaft 10 rotates more rapidly, the valve 22 will be operated more often and the pressure of the air in reservoir 26 will fall. Thus, in effect, the system serves to compute or integrate the operations of the valve member 22 and the number of rotations of the shaft 10 to cause the pressure within the reservoir 26 to be a resultant pressure determined by the speed of rotation of the shaft. At the same time, the pressure of the air or fluid impressed on the brake actuating cylinder 20 of the braking device will be determined by and substantially equal to that of the air in reservoir 26 but will be gradually varied due to the smoothing and damping action of capillary 38 and chamber 40. The pressure transmitted to the actuating cylinder 20 will, therefore, be a smoothly varying pressure which is inversely proportional of the speed of rotation of the shaft 10.

The relation between the pressure in chamber 26 and cylinder 20 and the tension applied to the web of material 2 can perhaps best be expressed mathematically by the equation where T represents the tension on the web 2, K is a proportionality constant determined by the type and adjustment of the braking elements or other control means employed, P is the pneumatic pressure in chamber 26 and the brake cylinder 20, and D is the diameter of the roll 4. However, the P can be expressed as P=K D where K is another proportionality constant determined by adjustment of the valve 22 and other elements of the system.

By substituting K D for P in the first equation The diameter of the roll 4 cancels out in this equation giving T=K K The tension applied to the web of material 2, therefore, will be constant at all times and determined by the adjustment of the valves, the type of control means used and other characteristics of the control system represented by K and K and will be independent of the diameter of the roll 4.

The control effected in this manner is continuous and automatic and does not introduce objectionable lag or variation in its application. Moreover, the control may be applied to either a brake or other means on the shaft 10 of the roll 4 as shown or it may be utilized to control the operation of motor 8 or any other element or combination of elements influencing the movement of the rolls or the tension applied to the material being handled.

It will be apparent that the operation of the valve 22 can be effected by a cam or other suitable means and it may be actuated by a flexible shaft or other driving connection for use at a remote point. Therefore, the sensing and control means may be positioned at any convenient location removed from the equipment to be controlled. Moreover, it may be readily applied to any form or type of web-handling equipment and can be changed from one machine to another with a minimum of time, labor and adjustment.

The form and type of the pressure-controlling valve or means employed in the system can be varied as desired. Thus, a needle valve, poppet valve, relay-operated valve or any other pressure-controlling means may be used. Similarly, the smoothing elements utilized to eliminate undesired pressure fluctuations or extraneous influences can be chosen to assure constant and uniform functioning of the system as required in any particular application.

The system further is capable of use when employing a hydraulic fluid in combination with a gas for actuating the control means. Thus, as shown in FIG. 2, the chamber 50 may be partially or wholly filled with a liquid 52 and a surge chamber 54 associated therewith to maintain a uniform but variable pressure on the liquid. The valve means 56 may serve to permit release of liquid from the chamber 50 or the valve means 58 may be employed to permit release of gas from the surge chamber 54. If

desired, both the valves 56 and 58 may be used.

In the alternative, the shaft 60 may serve to actuate a pump to force a limited amount of fluid into the chamber 5t) each time the shaft rotates whereby the air in surge chamber 54 will be compressed and the pressure increased as the speed of rotation of the shaft is increased. The relief valve then may be actuated to bleed otf fluid and prevent excessive pressure from building up in the chamber. The pressure variations in the system will be then directly proportional to the speed of rotation of the shaft and may be employed to reduce the braking effect as the speed of the shaft is increased. In any event, the control means in the system is actuated in a specifically determined relation to the speed of rotation of a shaft 60 of the machine to be controlled.

Further, as shown in FIG. 2, the fluid under controlled pressure from chamber 50 may be utilized to actuate a rheostat or other means 62 controlling the operation of a motor 64 or the braking means 66 on shaft 60 by which the roll 68 is carried, or a combination of such control means may be employed if desired. The fluid from the reservoir 50 may pass through restricting means 70 to its point of application as shown so as to further reduce or eliminate fluctuations in the pressure and assure continued and automatic control of the tension applied to the web of material 72.

While the invention has been described in FIG. 1 with particular reference to the use of compressed air supplied to the reservoir 26 by pump 30, it will be apparent that pump 30 may be a vacuum pump. In that event, the air in the chamber 26 will be maintained at subatmospheric pressure; and the valve 22 can be actuated to bleed a controlled amount of air into the reservoir 26. In this way, the subatmospheric pressure maintained in reservoir 26 and the force exerted on the braking elements 12 will be controlled automatically to maintain predetermined tension on the web of material. Thus, the system may be operated by using a vacuum or subatmospheric pressure instead of superatmospheric pressure as previously described.

It will thus be apparent that systems embodying the present invention are capable of many applications and variations in controlling the operation of web-handling and other equipment. In view thereof, it should be understood that the particular embodiments of the invention shown in the drawing and described above are intended to be illustrative only and are not intended to limit the scope of the invention.

I claim:

1. In combination with a machine having a roll from which material is to be unwound, means for placing said material under tension as it is unwound, and a shaft rotatable with said roll, a tension-controlling device comprising a gas reservoir, means for supplying gas under pressure to said reservoir, means for venting gas from said reservoir, means connected to said shaft for actuating said gas-venting means, and a control device operable in response to change in the pressure of gas in said chamber for varying the resistance to rotation of said shaft and roll.

2. In combination with a machine having a roll from which material is to be unwound and a shaft rotatable at a speed variable with the speed of rotation of said roll, means for controlling the tension applied to said material comprising a gas reservoir, means for supplying gas under pressure to said reservoir, means actuated by said shaft for venting gas from said reservoir, and means responsive to the pressure of the gas in said reservoir controlling the speed of rotation of said shaft.

3. Means for controlling the tension applied to a web of material as it is unwound from a roll rotatable with a shaft, said means comprising a shaft upon which a roll of material may be mounted, said shaft being rotatable with a roll of material thereon, a gas reservoir, a pump for supplying gas to said reservoir, a gas-venting valve communicating with said reservoir, means connected to said shaft for actuating said gas-venting valve to vent gas from the reservoir periodically in response to rotation of said shaft, braking means applied to said shaft and actuated by gas supplied thereto from said reservoir, and means interposed between said reservoir and braking means operable to suppress fluctuations in the pressure of the gas supplied to said braking means from said reservoir.

4. Means for controlling the tension applied to a web of material as it is unwound from a roll thereof rotatable with a shaft, said means comprising a shaft upon which a roll of material may be mounted, said shaft being rotatable with a roll of material thereon, a gas reservoir, a pump for supplying gas under pressure to said reservoir, a gas-venting valve communicating with said reservoir, a driving connection between said shaft and gasventing valve operable to actuate said valve to vent gas from the reservoir each time said shaft is rotated, braking means applied to said shaft and actuated by gas received from said reservoir, a flow-restricting means interposed between said pump and reservoir, and a capacity chamber and flow-restricting means interposed between said reservoir and braking means.

5. In combination with a machine having a roll from which material is to be unwound, means for placing said material under tension as it is unwound, and a shaft rotatable with said roll, a tension-controlling device comprising a fluid reservoir, means for supplying fluid under pressure to said reservoir, means for venting fluid from said reservoir, means connected to said shaft for actuating said fluid-venting means, and a control device operable in response to change in the pressure of fluid in said chamber for varying the resistance to rotation of said shaft and roll.

References Cited in the file of this patent UNITED STATES PATENTS 2,092,014 Pardee Sept. 7, 1937 2,569,670 Hollerith Oct. 2, 1951 2,631,791 Wheldon Mar. 17, 1953 2,843,228 Wysor July 15, 1958 3,036,787 Triquet May 29, 1962 

2. IN COMBINATION WITH A MACHINE HAVING A ROLL FROM WHICH MATERIAL IS TO BE UNWOUND AND A SHAFT ROTATABLE AT A SPEED VARIABLE WITH THE SPEED OF ROTATION OF SAID ROLL, MEANS FOR CONTROLLING THE TENSION APPLIED TO SAID MATERIAL COMPRISING A GAS RESERVOIR, MEANS FOR SUPPLYING GAS UNDER PRESSURE TO SAID RESERVOIR, MEANS ACTUATED BY SAID SHAFT FOR VENTING GAS FROM SAID RESERVOIR, AND MEANS RESPONSIVE TO THE PRESSURE OF THE GAS IN SAID RESERVOIR CONTROLLING THE SPEED OF ROTATION OF SAID SHAFT. 